The hydrant may be classified into a ground exposure type hydrant exposed on the ground, and an underground burial type hydrant buried under the ground.
In the ground exposure type hydrant, it is easy to couple the hydrant and a fire hose since the hydrant is exposed on the ground. However, there are problems that the hydrant may be damaged due to collision by a vehicle, etc. since the hydrant is exposed to external shock and may hinder traffic flow when not being used. Meanwhile, in the underground burial type hydrant, the hydrant is buried within a manhole and the top of the manhole is covered with a manhole cover. Therefore, there are advantages that this hydrant can prevent damage due to collision by a vehicle, etc. and does not prevent traffic flow. However, if the hydrant is used to in order to extinguish a fire, it is required that the manhole cover be opened and the fire hose be then connected to the hydrant within the manhole. Accordingly, this hydrant has a problem in rapidly responding to a fire.
Furthermore, in the conventional hydrant system as shown in FIG. 1, a hydrant 101 for supplying water for fire-fighting is disposed within a manhole 103 having a predetermined depth from the surface of the earth 102, which is covered with a manhole cover 112. A water-guide tube 105 is horizontally inserted into the manhole 103 and an opening/shutting valve 105a is disposed at the middle portion of the water-guide tube 105. A 90° elbow 106 that is curved vertically to the distal end of the water-guide tube 105 is coupled to a female cylinder 107. A male cylinder 108 has the outer circumference inserted into the inner circumference of the female cylinder 107. A T-shaped coupling pipe 109 is coupled to the top end of the male cylinder 108. A handle 109a for drawing the male cylinder 108 over the surface of the earth is formed on the coupling pipe 109.
In this structure, if a user wants to use the hydrant 101, the user holds the handle 109a formed on the T-shaped coupling pipe 109 at the top end of the hydrant 101 with hands and draws the handle upwardly. One side of the T-shaped coupling pipe 109 is covered with a cap 110 and the other end of the T-shaped coupling pipe 109 is screwed to a water-supply hose 111 in order to use water for fire-fighting. After the hydrant 101 is used, the opening/shutting valve 105a is locked and the water-supply hose 111 is separated from the T-shaped coupling pipe 109. Then, if the handle 109a is depressed, the male cylinder 108 returns to its original position due to its weight and the manhole 103 is covered with the manhole cover 112.
As above, if it is desired to use the conventional hydrant 101, the user has to uncover the manhole cover 112 of the hydrant and then draw the male cylinder 108 that is heavy, in a state where the handle 109a formed on the T-shaped coupling pipe 109 of the hydrant 101 is held with his or her waist bent. It gives a user inconvenience. Another user must couple the water-supply hose 111 to the drawn T-shaped coupling pipe 109. As such, in order to use the conventional hydrant, at least two persons are required. In order to solve this problem, there was disclosed technology wherein a spring is intervened between the female cylinder 107 and the male cylinder 108 in order to forcibly raise the male cylinder 108 by the resilient force of the spring. This technology is, however, relatively complicated in structure and thus increases the manufacturing cost. Further, since the hydrant is mounted in the underground at the side of a road, there is a problem that the spring may erroneously operate due to vibration of vehicles and moisture.
In addition, in the underground burial-type hydrant, water remaining in the cylinder after water for fire-fighting is used, may freeze in a cold weather. Due to this, in order to anti-freeze the frozen water in an emergency, a thawing device such as an electric resistor has to be used.